The Baltimore Longitudinal Study of Aging was initiated in 1958 (men) and 1978 (women). Storage of samples of blood or blood fractions began in 1963 and has been systematically continued since that time. Storage of multiple individual samples of serum, plasma, and, later of lyophilized plasma of whole blood (including leucocytes), and of erythrocytes is continuing. In addition, aliquots of 24-hr urinary collections have been stored. Samples have been removed for various approved protocols over the years. Most recently a longitudinal study of prostate-specific antigen was retrospectively performed. It showed that the longitudinal trajectory of the PSA concentration could detect prostatic carcinoma many years prior to usual clinical measures. Analyses of sex hormones were simultaneously measured on frozen samples. A comprehensive inventory of the "bank holdings" is now being conducted. An ancillary creation of a DNA bank is in the planning phase.